Quarterly report pursuant to Section 13 or 15(d)

Collaboration Arrangements - Additional Information (Detail)

v2.4.1.9
Collaboration Arrangements - Additional Information (Detail) (Merck KGaA, USD $)
In Millions, unless otherwise specified
3 Months Ended
Mar. 31, 2015
Mar. 31, 2014
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]    
Upfront and milestone payments received to date $ 110us-gaap_ProceedsFromCollaborators  
Merck KGaA's percentage share of worldwide development expenses 70.00%thld_WorldwideDevelopmentExpensesSharePercentage  
Revenue recognized by the Company 3.7us-gaap_DeferredRevenueRevenueRecognized 3.7us-gaap_DeferredRevenueRevenueRecognized
Company received a reimbursement for eligible worldwide development expenses 2.0us-gaap_RecoveryOfDirectCosts 5.9us-gaap_RecoveryOfDirectCosts
United States
   
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]    
Portion of profits that Company is eligible to participate, depending upon total sales 50.00%thld_PortionOfProfitsDependingOnSales
/ dei_LegalEntityAxis
= thld_MerckKGaAMember
/ us-gaap_StatementGeographicalAxis
= country_US
 
Regulatory and Development Milestones | Maximum
   
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]    
Potential future milestones 100thld_PotentialMilestonePayments
/ dei_LegalEntityAxis
= thld_MerckKGaAMember
/ us-gaap_RangeAxis
= us-gaap_MaximumMember
/ thld_RequirementOfEligibleFutureMilestonePaymentsAxis
= thld_RegulatoryAndDevelopmentMilestonesMember
 
Commercialization Milestones | Maximum
   
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]    
Potential future milestones $ 340thld_PotentialMilestonePayments
/ dei_LegalEntityAxis
= thld_MerckKGaAMember
/ us-gaap_RangeAxis
= us-gaap_MaximumMember
/ thld_RequirementOfEligibleFutureMilestonePaymentsAxis
= thld_CommercializationMilestonesMember